Helicopters are known which have a rotor comprising vanes caused to rotate about an axis perpendicular to their longitudinal direction; each section of the vane is thus driven with a linear speed relatively proportional to its distance from the axis of rotation. Under these conditions, the sustaining and/or propelling forces produced, relative to the swept surface, remain limited by aerodynamic phenomena (maximum speed at the tip of the vane, very low efficiency near the hub, . . . ) and it therefor follows that the energy efficiency of this type of rotor is limited (specific lift on the order of 40 to 50 Newtons per horsepower.)
Another type of rotor has been the object of study, and one can refer for example to the following patents which describe examples thereof: French patents 2,375,090, 2,309,401, 2,181,486 and 2,080,452. These rotors comprise profiled vanes or wings (hereinafter referred to as "profiled wings" by reason of their arrangement with respect to the flow of fluid which is similar to that of the wings of airplanes) which are caused to rotate about an axis parallel to their longitudinal direction. Under these conditions, each profiled wing section works under the same aerodynamic conditions (identical speed, incidence, circulation). One would therefor expect that this type of rotor would benefit from an aerodynamic efficiency which is much superior to that of helicopter rotors. However, in this type of rotor, each profiled wing is brought during its rotation to follow a rule or law of incidence which determines the performances of the rotor and the theory behind known rotors of this type directs a fixed rule of incidence, that is, one which repeats indefinitely, identically to itself: the relatively arbitrary choice of this rule (in particular imposed by technological constraints) cannot in any case in known rotors of this type, permit optimizing the efficiency when the operating conditions vary (speed of rotation of the rotor, speed of advance, relative incidence of the air . . . ). Further, these rotors of fixed kinetics are unusable in practice since, in the given operating conditions, they impose the intensity and/or the direction of the aerodynamic force produced and do not permit producing the necessary modulations for an effective steering of the aircraft. Further, even in the theoretical scheme, the prior documents which describe this type of rotor do not provide any suggestions which would permit adjusting the law of incidence to the desired forces.
The present invention seeks to overcome the deficiencies of known rotors of the aforementioned type having profiled blades or wings rotating about an axis parallel to the longitudinal direction of the profiled wings. The invention seeks to benefit fully from the advantages that may be expected from this type of rotor, in particular improved aerodynamic efficiency with respect to that of helicopter rotors.
One of the objects of the invention is in particular to provide an improved rotor having profiled wings or blades, the incidence of which is adjustable in real time according to a non-fixed rule.
Another object is to provide a process for steering said rotor, permitting at each instant controlling the rule of incidence of each profiled wing for obtaining sustaining and/or propelling forces desired at the moment considered, with an optimum energy efficiency.